Or you can modify you current android 4.1.2 and port it to 4.3. That is what I have done. I have manually upgraded my Android and now I am running self made Samsung stock 4.3 android. Checkout Screenshots.
http://imageshack.com/a/img46/1294/5z0x.jpg
http://imageshack.com/a/img513/3166/rtsd.jpg...